Popular keto and paleo diets aren’t helping your heart, report says
An analysis of various diets gave low marks to some of the most popular ones for straying from heart-healthy eating guidelines
By Anahad O’Connor
April 27, 2023 at 5:00 a.m. EDT
Ketogenic and paleo diets may be trendy, but they won’t do your heart any favors.
That’s the conclusion of a report from the American Heart Association, which analyzed many of the most popular diets and ranked them based on which approaches to eating are best and worst for your heart.
The authors said one of the purposes of their report was to counter widespread misinformation about nutrition promoted by diet books, blogs and people on TikTok, Instagram and Twitter — where posts promoting keto and paleo eating plans have surged in recent years.
The amount of misinformation that has flourished on social media sites has reached “critical levels,” said Christopher D. Gardner, the director of nutrition studies at the Stanford Prevention Research Center and chair of the committee that wrote the report.
“The public and many health-care professionals are likely confused about heart-healthy eating, and rightfully so,” he added. “Many of them likely feel that they don’t have the training or the time to evaluate the important features of the different diets.”
Ranking diets for heart health
The report, published Thursday in the journal Circulation, was drafted by a team of nutrition scientists, cardiologists, dietitians, and other health experts, who analyzed a variety of dietary patterns.
The diets were evaluated to see how closely they aligned with guidelines for heart-healthy eating, which are based on evidence from decades of randomized controlled trials, epidemiological research and other studies. The report also took into account factors like whether the diets allowed flexibility so that people could tailor them based on their cultural and personal preferences and budgetary constraints
The include advice to eat a wide variety of fruits and vegetables, whole grains like brown rice, bulgur, and steel cut oats, as well as lean cuts of meat and foods like olive oil, vegetable oils and seafood, which is high in protein and heart-healthy omega-3 fatty acids.
The group recommends limiting foods that are salty, sugary, highly processed or made with white flour and other refined grains. These include things like soft drinks, white bread, white pasta, cookies, cakes, pastries and processed meats such as hot dogs, sausages and cold cuts.
As for alcohol, the evidence that it provides a cardiovascular benefit is questionable. The heart association says that people who don’t drink shouldn’t start, and that if you do drink, you should limit your intake.
Popular low-carb diets scored lowest
The heart association gave its lowest rankings, using a scale of 0 to 100, to some of the buzziest diets widely touted on social media. These included very-low-carb regimens like the Atkins and ketogenic diets (31 points) and the paleo diet (53 points).
Following such diets typically requires restricting your carbohydrate intake to less than 10 percent of daily calories. The diets are widely promoted for weight loss and endorsed by many celebrities.
“People are so carb-phobic, and that’s one of the things that you see on Instagram — that carbs are bad,” said Lisa Young, an adjunct professor of nutrition at New York University, who was not involved in the report. “But that’s misinformation. Fruits, vegetables, legumes and whole grains are good for you — these are healthy carbs. These foods are the cornerstone of a healthy diet.”
The report noted that the Atkins and keto diets have some beneficial features: They restrict sugar and refined grains, for example, and they encourage the consumption of non-starchy vegetables like broccoli, asparagus, leafy greens, and cauliflower. But they generally require limiting a lot of “healthy” carbs that align with the heart association’s dietary principles, like beans, whole grains, starchy veggies, and many fruits. And they typically include a high intake of fatty meats and foods rich in saturated fat.
Some studies have found that very-low-carb diets can help with weight loss and improve certain markers of metabolic health, like blood sugar and triglyceride levels. But the heart association’s report noted that these improvements tend to be short-lasting, and that very-low-carb diets often cause an increase in LDL cholesterol levels, which can heighten the risk of heart disease.
The report found similar problems with the paleo diet, which excludes grains, vegetable oils, most dairy products and legumes such as peanuts and soybeans. The theory behind the diet is that it allows foods like fruit and honey that our hunter-gatherer ancestors had access to but excludes grains and other foods associated with modern agriculture.
The diets have also been criticized for what is often interpreted as an all-you-can-eat stance toward red meat, from steaks and burgers to bacon and processed deli meats. TikTok’s “Liver King,” for instance, gained popularity advocating a controversial meat-heavy “ancestral” diet consisting largely of organ and muscle meats.
The low ranking for the ketogenic and paleo diets is expected to generate controversy. In 2019, three doctors published an essay in JAMA Internal Medicine cautioning that the enthusiasm for the ketogenic diet was outpacing the science. The research was polarizing, generating a flood of emails of both support and condemnation.
Colette Heimowitz, vice president of nutrition and education at Atkins, said that the new report failed to adequately describe the Atkins diet, which includes three approaches with different carbohydrate limits.
One approach, which is typically used on a short-term basis for weight loss, allows only 20 grams of carbs per day. Another version of Atkins allows 40 grams of carbs per day, and the third approach allows people to have up to 100 grams of carbs daily, including small amounts of fruit, starchy vegetables, beans and whole grains. “Evidence suggests that Americans have varying tolerances to carbohydrate loads,” Heimowitz said. “So carb-focused dietary patterns like Atkins have never been more relevant.”
The four winning heart diets
The heart association gave its highest mark — a score of 100 — to the DASH pattern of eating, which stands for “dietary approaches to stop hypertension.” Developed by researchers at the National Institutes of Health in the 1990s, the DASH diet is widely endorsed by doctors, dietitians and other nutrition experts.
But it’s not exactly buzzworthy among celebrities and social media influencers. The diet emphasizes vegetables, fruits, whole grains, beans, legumes, nuts, seeds and low-fat dairy, while encouraging people to limit their intake of salt, fatty meats, added sugars and refined grains.
The DASH diet and three others with high scores were grouped into what the heart association called Tier 1. The others in the Tier 1 group included the pescatarian diet (92 points), the Mediterranean diet (89 points) and the vegetarian diet (86 points).
While these diets have small differences, they also share some common denominators — promoting fresh produce, whole grains, beans and other plants and whole foods. The pescatarian diet is similar to the vegetarian diet, but it allows seafood. The Mediterranean diet promotes moderate drinking, while the DASH diet allows alcohol but doesn’t encourage it.
“The conclusion that we came away with between these diets is that they’re all fine and very consistent with a heart-healthy diet,” Gardner said.
Vegan and low-fat diets
Gardner emphasized that the report judged diets based on how they are “intended” to be followed, not necessarily on how some people actually follow or interpret them.
For instance, a vegetarian can drink Coca-Cola and eat potato chips and a McDonald’s Egg McMuffin without the meat for breakfast. It’s a vegetarian diet, but not exactly a heart-healthy vegetarian diet, Gardner said.
“That’s not what we have in mind when we say people should follow a plant-based diet,” he added. “I know from doing these studies that people don’t always follow diets as they’re intended: They follow them based on misinformation.”
The report included two other tiers of dietary patterns. Vegan and low-fat diets were grouped into the second tier because they encourage eating fiber-rich plants, fruits and veggies while limiting sugary foods and alcohol. But the report noted that they are quite restrictive and can be difficult for many people to follow. The vegan diet, in particular, can increase the risk of developing a vitamin B12 deficiency and other problems
The third tier of diets received the second-lowest range of scores. This group included low-carb approaches like the South Beach and Zone diets, which limit carbs to 30 or 40 percent of daily calories, as well as very-low-fat diet plans such as the Ornish, Esselstyn and Pritikin programs, which restrict fat intake to less than 10 percent of daily calories.
These diets received lower scores because they limit or eliminate a number of healthy foods, the report found. People on low-carb diets, for instance, tend to eat less fiber and more saturated fat, while people on very-low-fat diets have to cut back on all types of fat, including the healthy unsaturated fats found in olive oil, avocados, nuts and seeds.
Despite giving some diets low scores, the report did find that all of the diets across every tier had four positive things in common: They encouraged people to eat whole foods, more non-starchy vegetables, less added sugar and fewer refined grains.
“If we could get Americans to do those four things, that would go a long way toward everyone eating a healthy diet,” Gardner said.